Originally Posted by ChrisSlicks

It's a 5x5 matrix yielding 20 different combinations of connections. The output transistors are turned on one by one (ground reference) to sense which inputs are active. But basically if you wire INPUT 2 to OUTPUT 5 via a switch with an in-line diode you will activate HEADLAMP 1 mode, and if you wire INPUT 3 to OUTPUT 4 you will get HEADLAMP 2 mode. I don't know what is different between these 2 modes so you will have to test it. For those trying to turn on the voltage signal to the fog light it looks like you can wire INPUT 4 to OUTPUT 5. There are no specs on the diode shown but it doesn't look like it is doing anything special other than regulating current flow in the right direction. A IN4001 (available anywhere) should do the trick.